Field of the Invention
This invention relates generally to a combined AM/FM and WiFi antenna assembly and, more particularly, to a combined AM/FM and dedicated short range communications (DSRC) system mast antenna assembly for a vehicle, where the mast antenna assembly is positioned on a vehicle roof and the DSRC system antenna is placed at a top end of the mast antenna assembly.
Discussion of the Related Art
Traffic accidents and roadway congestion can be significant problems for vehicle travel. Vehicular ad-hoc network based active safety and driver assistance systems are known that allow a vehicle communications system, such as a dedicated short range communications (DSRC) system, to transmit messages to other vehicles in a particular area with warning messages about dangerous road conditions, driving events, accidents, etc. In these systems, multi-hop geocast routing protocols, known to those skilled in the art, are commonly used to extend the reachability of the warning messages, i.e., to deliver active messages to vehicles that may be a few kilometers away from the road condition, as a one-time multi-hop transmission process. In other words, an initial message advising drivers of a potential hazardous road condition is transferred from vehicle to vehicle using the geocast routing protocol so that vehicles a significant distance away will receive the messages because one vehicle's transmission distance is typically relatively short.
Vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I), collectively known as V2X, communications systems of the type being described herein require a minimum of one entity to send information to another entity. For example, many vehicle-to-vehicle safety applications can be executed on one vehicle by simply receiving broadcast messages from a neighboring vehicle. These messages are not directed to any specific vehicle, but are meant to be shared with a vehicle population. In these types of applications, where collision avoidance is desirable, as two or more vehicles talk to each other and a collision becomes probable, the systems can warn the vehicle drivers, or possibly take evasive action for the driver, such as applying the brakes. Likewise, traffic control units can observe the broadcast of information and generate statistics on traffic flow through a given intersection or roadway.
Modern vehicles employ various and many types of antennas to receive and transmit signals for different communications systems, such as terrestrial radio (AM/FM), cellular telephone, satellite radio, DSRC, GPS, etc. Often the antennas used for these systems are mounted to a roof of the vehicle so as to provide maximum reception capability. Further, many of these antennas are often integrated into a common structure and housing mounted to the roof of the vehicle.
The design and style of a vehicle often requires that the vehicle roof have a curved configuration. It is known to mount the antenna for a DSRC system to the back part of the roof of the vehicle. In this configuration, the DSRC antenna may be at least partially blocked from a forward view because of a raised center portion of the vehicle roof, thus reducing antenna performance because there is more radiation from the antenna coming off the rear of the vehicle and less radiation coming off the front of the vehicle.